This invention relates to an adaptive error correction control system which includes a digital error correction system (DECS).
This invention relates particularly to an adaptive error correction control system which includes a DECS for optimizing mirror positioning in a spatial chopping or scanning telescope system.
The adaptive control of the present invention reduces control system error to near zero by anticipating a problem and feeding forward in time a correction to deal with the problem before it happens. The adaptive control is used in a controlled system of the kind which is cyclical in operation and which operates in response to repetitive cycle commands so that the operation of the system is substantially predictable for a significant number of cycles of operation.
Conventional analog feedback controls feed an analog error signal into a control loop which is designed to reduce and/or to eliminate the error. An analog feedback control loop of this kind can be effective to reduce error to a substantial extent; but the analog feedback control loop may not function satisfactorily when it is necessary to reduce the error to near zero.
An analog system, by its nature, does not remember anything; so it does not remember the history of a cycle. An analog system is reactive, whereas an error correction system which reduces error to near zero needs to be proactive. An error correction system which can reduce error to near zero needs to know what went wrong in the past so that it can feed forward in time a correction to deal with a problem before it happens. Such an error correction system needs to know exactly what error correction is needed at each point in a cycle of operation and needs to feed forward an appropriate correction and also to apply the correction at a time interval far enough in advance of the time when the correction is needed so as to balance the system dynamics.